 So the short-term energy cycle that we're going to be talking about today is the transfer or the harvesting of energy by phytoplankton from the surface ocean. So phytoplankton are photosynthetic organisms and so they harvest light along with nutrients and carbon dioxide and fix that as particular organic carbon. So it's carbon within their bodies. And this occurs over time frames of days to weeks. And there's a few groups of phytoplankton that photosynthesize in the polar oceans and in the tropical oceans. After they've finished photosynthesizing, they tend to die and either they get eaten by zooplankton or they sink out of the surface ocean, the sunlit surface ocean to the deep ocean. So this is the transfer of carbon and associated energy from the surface ocean to the deep ocean. The time scale of this can be from days to weeks and as they sink, they generally respire so they transfer that energy back into the deep ocean. And this is termed the biological carbon pump. The reason it's called a pump is it's the pumping against the gradient or the transfer of energy against the gradient. It's going from a high energy environment, so that's the surface ocean to an energy environment that's a bit lower in the deep ocean with respect to sunlight.